Some type of air-conditioning device has an indoor unit for accommodating an air blowing fan therein and a blow-out duct or a suction duct which is connected to the indoor unit, and blows out air from the air blowing fan. With respect to this type of air-conditioning device, there are various installation states among which the length of the blow-out duct or the suction duct is different, or under which an air suction grill facing a room space and an air blow-out grill are connected to each other through a duct or directly connected to each other through no duct. External static pressure (static pressure usable out of the machine) is varied in accordance with the installation state.
When the external static pressure varies, the relationship between the rotation number of the air blowing fan and the air volume (air volume characteristic) varies, so that it is required to change the rotation number of the air blowing fan in accordance with the variation of the air volume characteristic in order to obtain a proper air volume. In order to perform fan control to obtain a proper air volume, there has been proposed an air-conditioning device which controls the air blowing fan so as to obtain a perception air volume larger than an air volume used under normal operation, measures the shaft power of the air blowing fan under this control to obtain a characteristic of shaft power and air volume, and controls the fan on the basis of the thus-obtained characteristic (see Patent document 1, for example).